Short-term exposure to fine particulate matter constituents and mortality:case-crossover evidence from 32 counties in China

A growing number of studies associated increased mortality with exposures to specific fine particulate(PM_(2.5))constituents,while great heterogeneity exists between locations.In China,evidence linking PM_(2.5)constituents and mortality was extensively sparse.This study primarily aimed to quantify short-term associations between PM_(2.5)constituents and non-accidental mortality among the Chinese population.We collected daily mortality records from 32 counties in China between January 1,2011,and December 31,2013.Daily concentrations of main PM_(2.5)constituents(organic carbon(OC),elemental carbon(EC),nitrate(NO_(3)^(-)),sulfate(SO_(4)^(2−)),and ammonium(NH_(4)^(+)))were estimated using the modified Community Multiscale Air Quality model.Time-stratified case-crossover design with conditional logistic regression models was adopted to estimate mortality risks associated with short-term exposures to PM_(2.5)mass and its constituents.Stratification analyses were done by sex,age,and season.A total of 116,959 non-accidental deaths were investigated.PM_(2.5)concentrations on the day of death were averaged at 75.7μg m^(−3)(control day:75.6μg m^(−3)),with an interquartile range(IQR)of 65.2μg m^(−3).Per IQR rise in PM_(2.5),EC,OC,NO_(3)^(-),SO_(4)^(2−),and NH_(4)^(+)at lag-04 day was associated with an increase in non-accidental mortality of 2.4%(95%confidence interval,(1.0–3.7),1.7%(0.8–2.7),2.9%(1.6–4.3),2.1%(0.4–3.9),1.0%(0.2–1.9),and 1.6%(0.3–2.9),respectively.Both PM_(2.5)mass and its constituents were strongly associated with elevated cardiovascular mortality risks,but only PM_(2.5),EC,and OC were positively associated with respiratory mortality at lag-3 day.PM_(2.5)mass and its constituents associated effects on mortality varied among sex-and age-specific subpopulations.Differences in the seasonal pattern of associations exist among PM_(2.5)constituents,with stronger effects related to EC and NO_(3)^(-)in warm months but SO_(4)^(2−)and NH_(4)^(+)in cold months.Short-term exposures to PM_(2.5)compositions were positively associated with increased risks of mortality,particularly those constituents from combustion-related sources.